The present invention relates generally to cooling systems for heat-generating devices and, more particularly, to a modular spray cooling system and a method of using the spray cooling system to cool a semiconductor device.
With the advent of semiconductor devices having increasingly large component densities, the removal of heat generated by the devices has become an increasingly challenging technical issue. Extrapolating the ongoing changes in microprocessor organization and device miniaturization, one can project future power dissipation requirements of 100 W from a 1 cm by 1 cm core CPU surface area within the easily foreseeable future.
Highly available computer systems, to prolong a customer""s investment, are designed to both be maintained for long periods and to be easily maintained over time. This makes it preferable that a computer system is well cooled across all of its components on each board, and that the computer can quickly and readily accept replacements for malfunctioning boards. Typical processor boards sometimes include multiple CPU modules, application-specific integrated circuits (ICs), and one or more types of memory such as static random access memory (SRAM), as well as dcxe2x80x94dc converters, all of which have different and extreme power dissipation requirements. Adding to the complexity, the variety of chip types on typical processor boards provides for chip surfaces at a variety of heights off the board""s surface.
In the past, the low power dissipation of the processors accommodated the use of low cost, air-cooled heat sinks that require minimal re-design effort. However, with higher dissipation requirements come more complex cooling systems that make both the even cooling requirements and the serviceability of a board a more complex issue. In particular, different components stand up off the board with different heights, which causes board-wide cooling systems to cool different components to different degrees, even if the components"" power dissipation levels are similar, which typically is not the case.
Spray cooling technologies, such as are described in U.S. Pat. No. 6,205,799, which is incorporated herein by reference for all purposes, can offer high dissipation levels that meet extreme cooling requirements. With reference to FIG. 1, in spray cooling, an inert spray coolant from a reservoir 11 is preferably sprayed by sprayers 13 onto chips 15 mounted on a printed circuit board 17. The coolant preferably evaporates, dissipating heat within the chip. The sprayers and chips, and the board, are mounted within sealed cases 19 fixed within a computer system. The sprayed coolant is typically gathered and cooled within a condenser 21, and then routed back to the reservoir by a pump 23.
The cases are evacuated systems with robust closure systems. Access to the components for maintenance can typically be had only through extensive disassembly of the computer system and case, which is significantly more time consuming and costly than the maintenance of standard air-cooled chips. Thus, for a liquid cooled board, board replacement becomes a complex issue that must deal with the presence of liquid, and potentially the need for an evacuated system.
Furthermore, it is known that the thermal performance achieved from spray cooling is dependant upon the distance between the firing nozzle and the hot surface. A greater distance allows for more of the cooling fluid to evaporate prior to reaching the chip. Furthermore, drag reduces the speed of the droplets, allowing even more cooling fluid to evaporate prior to reaching the chip. The evaporation of cooling fluid prior to reaching the chip reduces the fluid flow rate received by the chip, and thus reduces the thermal performance of the spray cooling system. The reduced speed of the droplets also reduces their momentum, and thus their ability to penetrate vapor barriers, such as can form at near-maximum levels of heat flux for a spray-cooling system.
Since processor boards can and often do contain components of dissimilar heights, it has been suggested that the hottest component be used as the reference component to determine the sprayjet cartridge-to-board spacing. The primary disadvantage of this technique is that fluid may be delivered inefficiently to other hot components of markedly different heights from the reference component.
Accordingly, there has existed a need for an easily maintainable spray cooling system that maximizes spray cooling efficiency for a plurality of components on a single printed circuit board. Preferred embodiments of the present invention satisfy these and other needs, and provide further related advantages.
In various embodiments, the present invention solves some or all of the needs mentioned above by providing a cooling system that efficiently operates on one or possibly more high-dissipation devices with relatively simple maintenance.
The invention can include or form a modular sprayjet cooling system configured for cooling one or more components (e.g., electrical components) on a board by spraying the one or more components with a cooling fluid during the components operation. The invention features an enclosure that defines an internal chamber configured to contain the board. An electrical connector within the chamber is configured to electrically connect to the board, enabling the operation of the components. A sprayer is located within the chamber, and it is configured to spray one or more of the components with the cooling fluid to cool them. During operation, the chamber is closed and sealed such that cooling fluid cannot leak out of the chamber.
A feature of the invention is that the chamber can be readily opened and closed by hand for external access to the chamber. When the chamber is opened, the board can be readily removed and replaced, by hand or with mechanical or electro-mechanical assistance, without risk of interfering with the operation of the rest of the electronic system containing the modular sprayjet cooling system. This feature provides for efficient replacement of the board, potentially without shutting down the entire system of which the board is apart. Thus, the invention allows for hot-pluggable replacement boards that are spray cooled.
Another feature of the invention is that the enclosure can be configured for releasably inserting into a bay of an electronic device, the bay having an electrical connector. The enclosure includes a second electrical connector on the exterior of the enclosure, configured to mate with the electrical connector of the bay to place the board in communication with the electronic device via the first electrical connector. This feature provides for efficient replacement of the board, potentially without shutting down the entire system of which the board is a part.
Also, the invention can include or form a sprayjet cooling system for cooling one or more components on a board during operation of the components. In particular, the invention features first and second sprayers configured to spray the one or more components on the board with the cooling fluid. The invention further features an adjustment mechanism configured to support the first sprayer at a distance from the board that is adjustable relative to the distance between the second sprayer and the board. Advantageously, these features provide for efficient and effective cooling of the components on the board, taking each components height into consideration.
Other features and advantages of the invention will become apparent from the following detailed description of the preferred embodiments, taken with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The detailed description of particular preferred embodiments, as set out below to enable one to build and use an embodiment of the invention, are not intended to limit the enumerated claims, but rather, they are intended to serve as particular examples of the claimed invention.